Current AMPS MM5 Configuration

For recent changes, see History.

Vertical Coordinate:

MM5 uses a terrain-following vertical coordinate, defined according to


sigma = (Pref - Ptop) / (Ps - Ptop)

where:

Pref	is a reference-state pressure.
Ptop	is a reference-state pressure defining the model top.
Ps	is a reference-state surface pressure.


sigma has a value of 1.0 at the surface, and 0.0 at the model top.

The reference state referred to above is a horizontally-homogeneous atmosphere defined according to five constants:

P0	: Reference Sea-level pressure.
TLP	: Reference temperature lapse rate. (delta T / delta ln(p) )
TS0	: Reference sea-level temperature.
TISO	: Reference stratospheric temperature.
Ptop	: Reference pressure of the model top.


In the AMPS MM5 configuration, the following values are used:

P0	= 100000 Pa
TLP	= 50 K
TS0	= 265 K
TISO	= 210 K
Ptop	= 5000 Pa

Vertical Grid:

MM5 uses a staggered vertical grid, with half-sigma levels defined halfway between full-sigma levels.

The AMPS MM5 configuration features 32 full-sigma levels and 31 half-sigma levels, specified as follows:



half-sigma index half-sigma level 31 0.998250 30 0.994750 29 0.990750 28 0.985625 27 0.979125 26 0.971000 25 0.961000 24 0.948875 23 0.934375 22 0.917250 21 0.927500 20 0.897125 19 0.873375 18 0.845375 17 0.812875 16 0.735250 15 0.691125 14 0.644125 13 0.595000 12 0.545000 11 0.495000 10 0.445000 9 0.395000 8 0.345000 7 0.295000 6 0.245000 5 0.195000 4 0.145000 3 0.100000 2 0.060000 1 0.020000

full-sigma index full-sigma level 32 1.00000 31 0.99650 30 0.99300 29 0.98850 28 0.98275 27 0.97550 26 0.96650 25 0.95550 24 0.94225 23 0.92650 22 0.90800 21 0.88625 20 0.86050 19 0.83025 18 0.79550 17 0.75650 16 0.71400 15 0.66825 14 0.62000 13 0.57000 12 0.52000 11 0.47000 10 0.42000 9 0.37000 8 0.32000 7 0.27000 6 0.22000 5 0.17000 4 0.12000 3 0.08000 2 0.04000 1 0.00000

Horizontal Grids:

The AMPS MM5 configuration features six grids as follows (see Maps):



GRID	x dimension	y dimension	Grid Cell Size (km)	Start (hour)	End (hour)	Timestep (seconds)
1	110	145	90	0	120	240.0
2	220	208	30	0	120	80.0
3	79	94	10	6	36	26.7
4	85	85	10	6	36	26.7
5	85	115	3.3	6	36	8.9
6	172	151	10	6	36	26.7


Nests are run in two-way interactive mode, using 1-point feedback with heavy smoothing (IFEED=4).

Options (Physics parameterizations, mostly):

Radiation:

CCM-2 radiation adapted for MM5 and for Polar conditions (IFRAD=3) Updated every 30 minutes. (RADFRQ=30)

Boundary Layer:

Eta PBL parameterization, adapted for MM5 and for Polar conditions. (IBLTYP=4)

Soil Model:

Multi-layer soil model, adapted for polar conditions (ISOIL=1),

Microphysics:

Mixed-phase microphysics, without graupel. (IMPHYS=5)

Cumulus Parameterization:

Grell cumulus parameterization (ICUPA=3) on grids 1 through 4.
Beginning with the 2002120412 forecast, no cumulus parameterization on grid 5. (Before 2002120412, Grell scheme was used on grid 5.)

Vertical Advection:

Vertical moisture advection uses linear interpolation (IVQADV=1).
Vertical temperature advection uses linear interpolation (IVTADV=1).
Vertical temperature advection and adiabatic term use potental temperature (ITHADV=1).

Vertical Diffusion:

Dry vertical diffusion. (IMVDIF=0)
Diffusion done with perturbation temperature. (ITPDIF=1)

Upper Boundary Condition:

Model top at 50 mb; 8-layer sponge/nudging to AVN forecasts following
OSU/BPRC methods.

Namelists:

For reference, here are the current INTERPF namelist and MM5 namelist used for AMPS.